Fix `jekyll serve --limit_posts n` failed

lib/jekyll/site.rb

@@ -27,7 +27,8 @@ module Jekyll
       self.include         = config['include']
       self.future          = config['future']
       self.show_drafts     = config['show_drafts']
-      self.limit_posts     = config['limit_posts']
+      # given as String if it is came from CLI option
+      self.limit_posts     = config['limit_posts'].nil? ? nil : config["limit_posts"].to_i
       self.keep_files      = config['keep_files']
 
       self.reset

test/test_generated_site.rb

@@ -68,5 +68,15 @@ class TestGeneratedSite < Test::Unit::TestCase
         @site = Site.new(Jekyll.configuration)
       end
     end
+
+    should "ensure if limit_posts is a String (from CLI option)" do
+      clear_dest
+      stub(Jekyll).configuration do
+        Jekyll::Configuration::DEFAULTS.merge({'limit_posts' => "3"})
+      end
+      @site = Site.new(Jekyll.configuration)
+
+      assert_equal 3, @site.limit_posts
+    end
   end
 end